The present invention relates to a small DC brushless fan.
An information related equipment (hereafter referred to as xe2x80x9cequipmentxe2x80x9d) is desired to have a high performance, a small size, and a high density. In order to meet such requirements, equipment manufacturers are attempting to build smaller electronic components of a higher performance into the equipment and to produce wiring substrates that are multilayered so as to densely integrate the electronic components thereinto and that have a high productivity with high density, temperature rise due to heat from the electronic components becomes greater.
A blowing fan is normally used-to cool the equipment, but local cooling of substrates is more and more frequently carried out due to the increasing need to efficiently cool the equipment with a low power consumption. Such a local cooling fan is disclosed, form example, in Japanese Utility Model Laid-Open No. 62-195356. This application provides a box-shaped axial fan having screws located in corresponding corners thereof and comprised of motor feeding terminals so that the electric connection of the fan can be completed by simply fixing the fan to a printed circuit board by using machine screws. However, many conventional blowing fans, including the above example, depend on the concept that the fan is mounted on a rear surface of an enclosure of the equipment, and do not have an optimal form for locally cooling substrates.
In view of these backgrounds, the requirements of fans for locally cooling substrates will be listed below. First, the fan must be able to be located close to electronic components that tend to be very hot. To achieve this, the fan is desirably very small enough to be mounted adjacent to electronic components. In addition, the fan must be consistent with improvement of the degree of integration of the equipment on the substrate. Thus, it can desirably be mounted by using the surface mount technology similarly to other solid electronic components. This is because the degree of integration of a multilayer substrate decreases when holes are formed in the substrate so that terminals can be passed therethrough. In addition, for an improved degree of integration, the fan desirably has such a form as to be mounted close to adjacent electronic components to achieve a high density.
Secondly, to increase the productivity of the equipment, the fan must be compatible with the same mounting process as other solid electronic components. To meet this requirement, the fan desirably has a form suitable for the reflow soldering method. The fan also desirably has such a form as to be efficiently mounted using the same assembly machine as other solid electronic components.
Thirdly, the fan must be compatible with the portable use of the equipment. To achieve this, the fan desirably has a high impact resistance.
It is an object of the present invention to meet the above requirements. That is, a first object is to contribute to improving the degree of integration of the equipment. To attain this object, the fan must be small enough to be mounted adjacent to electronic components, must be able to be mounted on the substrate of the equipment using the SMT technology, and must have such a form as to be mounted close to adjacent electronic components to achieve a high density.
A second object is to contribute to improving the productivity of the equipment. Thus, the fan must have a form suitable for the reflow soldering method and must have such a form as to be efficiently mounted using an assembly machine.
A third object is to accommodate the portable use of the equipment. To meet this object, the fan must have a sufficient impact resistance.
A general object of the present invention is to attain the above objects to provide equipment that has a smaller size, a lower weight, a higher productivity, and a higher added value.
To attain this object, a DC brushless fan according to the present invention is comprised of: a housing comprising a bottom surface, a side surface, anda top surface, the bottom surface being located adjacent and opposite to a substrate of an equipment; pairs of terminals provided on an outer side of the bottom surface and having a function of being mechanically or electrically soldered to the substrate of the equipment, wherein there are provided a stator, a bearing device, and a rotor inside the housing, the rotor being supported by the bearing device and opposed to the stator, the fan further comprising a blowing fan rotating with the rotor.
Next, the structure of the DC brushless fan according to the present invention will be described in detail.
First, a DC brushless fan according to a first mode of the present invention is configured so as to meet the following requirements:
(a) The DC brushless fan has a housing comprising a bottom surface, a side surface, and a top surface.
(b) The bottom surface is located adjacent and opposite to a substrate of an equipment, and pairs of terminals are provided on the outer side of the bottom surface and having a function of being mechanically or electrically soldered to the substrate of the equipment.
(c) A stator, a bearing device, and a rotor are provided inside the housing.
(d) The rotor is supported by the bearing device and opposed to the stator, and the fan includes a blowing fan rotating with the rotor.
Such terminals serve to reduce the size of the fan and enable the fan to be joined (soldered) with a top surface of the substrate of the equipment by using the reflow method. The housing also allows the DC brushless fan to be handled easily. When the terminals on the bottom surface side are formed so as not to project from the side surface beyond the bottom surface area, the fan can be placed close to adjacent electronic components. In addition, the terminals can be further projected in a vertical direction from the bottom surface so as to engage with holes in the substrate of the equipment. Essentially, however, the form in which the terminals are surface-connected to a surface of the substrate is desirable in improving the mounting density of the equipment.
A DC brushless fan according to a second mode of the present invention is configured so as to meet the following requirements:
(a) The DC brushless fan has a housing comprising a bottom surface, a side surface, and a top surface.
(b) The bottom surface is located adjacent and opposite to a substrate of an equipment, and pairs of terminals project from the side surface at generally the same height as the bottom surface and have a function of being mechanically or electrically soldered to the substrate of the equipment.
(c) A stator, a bearing device, and a rotor are provided inside the housing.
(d) The rotor is supported by the bearing device and opposed to the stator, and the fan includes a blowing fan rotating with the rotor.
Since the terminals project from the side surface, these terminals can be added to the terminals arranged in the bottom surface area to further increase the number of terminals, thereby increasing the binding strength. This form can accommodate the reflow method for locally heating the projecting terminals.
A DC brushless fan according to a third mode of the present invention is configured so as to meet the following requirements:
(a) The DC brushless fan has a housing comprising a bottom surface, a side surface, and a top surface, and the housing includes a chuck section.
(b) The bottom surface is located adjacent and opposite to a substrate of an equipment, and pairs of terminals are provided on the bottom or side surface side and having a function of being mechanically or electrically soldered to the substrate of the equipment.
(c) A stator, a bearing device, and a rotor are provided inside the housing.
(d) The rotor is supported by the bearing device and opposed to the stator, and the fan includes a blowing fan rotating with the rotor.
Such a housing enables the fan to be transferred using a transfer and load chuck of an electronic automatic assembly machine, thereby enabling the fan to be automatically loaded on and soldered to the substrate of the equipment. The chuck section desirably accommodates a suction chuck, a gripping chuck, or a magnet chuck, as shown below.
In addition, according to the DC brushless fan of the present invention, the chuck section is a suction surface of the fan, that is, the top surface thereof to which the suction chuck can be opposed. Such a suction surface enables the fan to accommodate a suction chuck, which is most often used for electronic components assembly machines. When the suction surface that is the top surface is a flat surface having a diameter of 3 mm or more, desirably 4 mm or more, the fan is compatible with most automatic assembly machines. The suction surface may be shaped like a ring. Either an inclined surface or a spherical surface can be chucked.
In addition, according to the DC brushless fan of the present invention, the chuck section is two parallel planes extending generally perpendicularly to the bottom surface or two parallel ridges located on the side surface and extending parallel with the bottom surface. These two parallel planes on the side surfaces allow the use of electronic components assembly machine for gripping, transferring, and aligning the DC brushless fan and checking the alignment. The fan can also be aligned by using a gripping chuck to clamp it at the two parallel ridges extending parallel with the bottom surface.
In addition, according to the DC brushless fan of the present invention, the chuck section is the top surface comprised of a ferromagnetic member. Such a ferromagnetic member in the top surface enables the fan to be transferred using an electronic components assembly machine with a magnet chuck. Preferably, the ferromagnetic member is, for example, a plated steel plate or a magnetic stainless steel plate.
Further, according to the DC brushless fan of the present invention, marking or direction determination means is provided on the top or side surface and adapted for enabling a mounting direction of the fan to be determined. Such a marking, which enables the mounting direction to be determined, enables the fan to be transferred and loaded by using an automatic assembly machine. In this place, the marking may have an optical reflectance different from that of its peripheral area, may exhibit a magnetic reaction different from that of the peripheral area, or may be projected or recessed relative to the peripheral area. One of these methods is selected depending on the structure or size of the DC brushless fan or the configuration of an equipment assembly facility. The direction determination means is obtained by forming a part of the housing into a shape different from that of the remaining part.
In addition, according to the DC brushless fan of the present invention, the number of terminals located on the bottom surface is larger than the number of poles required for electric connections. Thus, since many terminals including those required for electric connections are provided on the outer side of the bottom surface, the mounting strength of the DC brushless fan on the substrate is increased to improve the impact resistance. The basic concept is that in any DC brushless fan, the terminals must have a firm mechanical junction function for supporting principal weights. The terminals maybe formed of lands, plates, lines, or headed pins. The bottom surface needs not be a bottom-surface-side front surface and must only be formed substantially of a bottom-surface-side end surface of a side wall.
Furthermore, according to the DC brushless fan of the present invention, the pairs of terminals are arranged on the bottom surface on both sides of a line passing through the centroid or the center of gravity of the bottom surface. In this manner, the terminals are arranged so as not to be biased toward one portion of the bottom surface, so that the terminals cooperate to effectively support an impact, thereby providing a large holding force. Desirably, the terminals are arranged point-symmetrically, line-symmetrically, or rotation-symmetrically relative to the centroid or the center of gravity of the bottom surface in order to share an impact more evenly. More specifically, the center of gravity is a point at which the center of gravity of the entire fan is projected vertically onto the bottom surface.